Developing software applications can be a complicated process. Most applications use front ends that are well known to developers. However, connecting to a back-end system requires knowledge of how to interface with the back-end system. For example, a developer has to know the schema and business logic associated with the back-end system. Developers who are not familiar with the back-end system will have a steep learning curve when developing applications that interface with the back-end system. Furthermore, a developer who is not familiar with a back-end system may be able to accidentally harm the back-end system.
By not being familiar with the business logic, and having a steep learning curve, the cost of development is increased and applications may be more error prone than using developers who are familiar with the back-end system.